Lubricating composition containing boric acid



Patented Oct. 21, 1952 UNITED sT-ATE LUBRICATING ooMPosrrIoN CONTAINING I f T BORIC 011) David L. Cook, El Cerrito, Califgassignor to Shell u Development Company, Emeryville, Calif., a

corporation of Delaware No Drawing.

mobile trades that a dirty engine, that is, one

that has been in substantial use to. form deposits on. the piston crown, valves, and walls of the combustion chamber, requires a gasoline of higher octane rating in order not to knock than is required by a new or clean engine. In other words, the octanevalue of a gasoline demanded by such a dirty engine in order not to knock (referred to as octane demand) is higher than the octane demand of a clean engine. For example, a clean engine which requires a gasoline having an octane rating of 60 in order not to knock is said to have an octane demand of 60. If the same engine when dirty requires, gasoline having an octane rating of 75 in order not to knock, such a dirty engine is said to have an way of contrast, the present invention is con-.

cerned with the development of a lubricant composition which has the effect of preventing increase in the octane demand of an engine on prolonged operation. These lubricant compositions are also effective in reducing the octane demand of an engine which has attained an increased demand by prior operation in the absence of such lubricants.

It has now been found that lubricating compositions containing boric acid have outstandingly useful properties, among which is the ability to prevent or materially reduce the in crease in octane demand of a spark ignition internal combustion engine.

The lubricant base used in preparing the present compositions is preferably a mineral lubricating oil, but synthetic lubricants or mixtures of mineral oils and synthetic lubricants may also be used.

Boric acid is dispersed, either in solution or in suspension, in the lubricant base. In the case of solutions of boric acid in mineral oils, the solubility is very low so that in general a mutual solvent for the boric acid and oil will be required in order that a reasonably high concentration of the boric acid may be dissolved in the oil.

Suspensions of boric acid in the lubricant may be prepared either by dispersing the solid in the Application October 25, 1.951, Serial No. 253,223

Claims. (Cl. 252-18) lubricant, such as by grinding the combination in a paint mill, colloid mill or the like, or by precipitation from a supersaturated solution. The supersaturated solutions may be obtained, for example, by cooling a solution previously saturated at an elevated temperature. Or an amount of boric acid in excess of its normal solubility may be dissolved in the lubricant by means of a volatile cosolvent, so that evaporation of the cosolvent will give a supersaturated solution-of boric acid in the lubricant. Care must be exercised in that the suspended boric acid particles must be sufliciently small in size and sufficiently well dispersed that the composition will not tend to agglomerate or settle and clog oil lines, filters, etc. In order to stabilize the foregoing suspensions, dispersing agents can be used. Suitable dispersing agents are, for example, the'petroleum sulfonates, particularly the 'alkali and alkaline earth metal sulfonate such as sodium or calcium petroleum sulfonates, phosphatides such as animal lecithin, and long chain carboxylic acid esters, partial or complete, of polyhydric alcohols, e. g., glycerol mono-oleate or glycerol sorbitan laurate. Theconcentration of the dispersing agent in the oil will depend upon the concentration of the boric acid to be dispersed and upon the particular dispersing agent used, but will generally be between about 0.01% and about 10% by weight. l I v In general, the mineral oil or other lubricant base will comprise greater tha'ri 90% or 95% one minute operation at full speed,

or more of the present lubricant compositions. The amount of boric acid dispersed therein will usually range from about 0.05% to about 2% by weight, although for specialized purposes, the concentration may be as low as 0.01% and as high as 5-or even 10%.

The lubricants can also contain appreciable quantities of other commonly used additives such as anti-oxidants (e. g., aromatic amines, alkylated phenols, etc.), corrosion inhibitors (e. g., fatty acid esters of polyhydric alcohols, petroleum sulfonates, etc.), detergents (e. g., metal soaps of fatty acids, naphthenates, phenates, etc.), sludge inhibitors, pour-point depressants, antifoam agents, viscosity index improvers, color stabilizers, and the like.

The following examples illustrate the invention more specifically:

Example I A single cylinder Lauson engine was operated under cyclic conditions, the cycle consisting of (1050 R. P. M.) and closed throttle, followed by three minute operation at full speed and half throttle with a 0.3 kilowatt load. The water jacket temperature was maintained at 160 F. and the oil sump temperature was maintained at F. The

3 clean engine octane demand was determined to be 60. After operation with isooctane fuel and an. uncompounded SAE 30 mineral lubricant oil, the octane demand rose to an apparent equilibrium value of 68. The uncompounded lubricant was then drained from the crankcase and re.-

The above testing procedure was repeated except that the water jacket temperature was maintained at about 212 F. and the oil sump temperature was maintained at about 225 F; As in Example I, the octane demand which was built'up by operation with an uncompounded lubricant and isooctane fuel was reduced by operation with the lubricant containing boric acid.

Ewample III The test described in Example II was continued except that a typical automotive fuel containing 2.8 cc. of tetraethyl lead per gallon was substituted for the isooctane as the fuel. The octane demand remained low as long as the boric acid-containing lubricant was utilized.

Example IV When the above tests are carried out using typical automotive lubricants containing (in addition to boric acid), commonly used detergents, anti-oxidants, corrosion-inhibitors, etc., substantially the same results are obtained.

Example V About 0.2% by weight of boric acid was dispersed in a mineral lubricating oil with the use of calcium petroleum sulfonates (0.2% S. A.).

This lubricant, in addition to giving the usual excellent results with respect to octane demand in engine tests, had good stability characteristics, there being no noticeable settling of the suspension even after prolonged standing.

While the present invention is particularly directed to lubricant compositions suitable for use in spark ignition internal combustion engines, it should be recognized that these lubricants are also useful for other uses, such as gear lubricants, drawing lubricants, and the like. In such cases, additional additives, such as extreme pressure agents, anti-wear agents, etc., are often incorporated into the lubricants.

I claim as my invention:

1. A lubricating composition comprising at least 90% of a mineral lubricating oil containing dispersed therein from about 0.05 to about 2 wt. per cent of boric acid.

2. A lubricating composition comprising a predominant amount of a lubricating oil containing dispersed therein between about 0.01. and about 5 wt. per cent of boric acid.

3. A lubricating composition comprising a predominant amount of a lubricating oil and from about 0.01 to about 10 wt. per cent of boric acid.

4. A lubricating composition comprising a predominant amount of a lubricant base, from about 0.01 to about 10 wt. per cent of boric acid, and a minor amount of a dispersing agent for said boric acid.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Lyons May 2, 1939 Number 

1. A LUBRICATING COMPOSITION COMPRISING AT LEAST 90% OF A MINERAL LUBRICATING OIL CONTAINING DISPERSED THEREIN FROM ABOUT 0.05 TO ABOUT 2 WT. PER CENT OF BORIC ACID. 